AT&T 950 - Manual (Page 7)

Set local area code
You can program up to four local area codes.
Calls outside your area
For: You dial: Enter in step 2:
All calls outside 11 digits No local
your area code (1 + area code +
phon e number)
area code
Some calls 10 digits Area codes
outside your (area code + that do not
area code phone number) require a 1
if you dial 10 digits (area code + phone number) for calls within your own
area code, include your area code as a local area code.
I. Press and release I opnows I until the screen displays:
Use the keypad to enter the three digits of the first
local area code. Press \ options ] to advance
to set the next local area code (LRC2-, LFIC3-,
LRC4-).
Press ¡OPTIONS] to save the settings when you have
finished entering local area codes.
O NOTE: if you do not need to program a local area
code, continue pressing i options l until the SET CLOCK
screen appears.